Cellular telephones may operate under a variety of standards including the code division multiple access (CDMA) cellular telephone communication system for which a 2nd generation system is described in TIA/EIA, IS-95, Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System, published July 1993 and a 3rd generation system is described in TIA/EIA, IS-2000-A Volumes 1 through 6. CDMA is a technique for spread-spectrum multiple-access digital communications that creates channels through the use of unique code sequences. In CDMA systems, signals can be and are received in the presence of high levels of interference. The practical limit of signal reception depends on the channel conditions, but CDMA reception in the system described in the aforementioned IS-95 Standard can take place in the presence of interference that is 18 dB larger than the signal for a static channel. Typically, the system operates with a lower level of interference and dynamic channel conditions.
A mobile station utilizing one of the CDMA standards utilizes a set of reverse channels to transmit data to the infrastructure and a set of forward channels to receive data from the infrastructure. Reverse channels include but are not limited to an Access Channel and one or more Traffic Channels. The Access Channel is used by mobile stations for communicating usually short messaging signals to a specific base station, where such signals include but are not limited to call originations, responses to infrastructure pages and system registrations. The various Access Channel messages are comprised of a message body, a message length indicator and a cyclic redundancy check (CRC). Access Channel messages are contained in a data structure called an Access Probe. An Access Probe comprises a preamble and an Access Channel message. Access Probes are sent in sequences containing the same message until an acknowledgement to the message is received. A mobile station will usually increase the power of each successive Access Probe until it receives an acknowledgment to the message or the access parameters affecting transmit power are modified by the base station. The entire process of sending one Access Channel message and receiving (or failing to receive) an acknowledgment is known as an Access Attempt.
A typical mobile-originated connection setup scenario involves the use of multiple signaling messages on multiple channels. The mobile station detects input from the user, for example through keypad or voice detection. The mobile station then initiates an Access Attempt by transmitting an origination message encapsulated in a sequence of Access Probes to a base station. The mobile station will continue transmitting Access Probes containing the same origination message until it receives an acknowledgement on the Forward Paging Channel from the base station that the Access Probe was transmitted to. When the base station receives one of the Access Probes, and resources are available, it responds by setting up a Forward Traffic Channel (defined by an orthogonal code such as a Walsh Code, or a Quasi-Orthogonal Function), transmitting null traffic data on the traffic channel and transmitting a channel assignment message (including the acknowledgement) on the Paging Channel. However, if resources are not readily available, the base station will transmit the acknowledgement along with Access Parameter instructions to the mobile station on the Paging Channel. Access parameter instructions can include, but are not limited to, changes in persistence parameters, access probe power parameters, acknowledgement timeout parameters, number of access probes per sequence or other well known access parameters. The mobile station will continue its Access Attempt, as modified by the Access Parameter instructions received from the base station, until a connection is established.
The connection scenario described above can require many messages and, hence, can consume a large amount of network capacity. Therefore, any way of consolidating this process, thereby conserving capacity, would be welcomed by network operators and be appreciated by users due to fast connection setup.
As discussed above, connection setup can be a process involving multiple reconnection attempts by the mobile station utilizing several Access Probe sequences. It can also involve base station adaptation of Access Parameters, especially when network resources are limited. An Access Probe containing an origination message generally contains a preamble and the origination message which contains information regarding what type of connection is being requesting, the capabilities of the requesting mobile station and other overhead parameters. The base station must manage the access channel parameters and traffic channel assignments based on a very limited knowledge of a particular mobile station state. This invention provides a way for a base station to intelligently adapt access parameters and manage channel assignments based on individual mobile station information.